1. Field of the Invention
The present invention is directed to a device and method for determining the volume of intervertebral disc augmentation material needed to complete disc augmentation and the material's subsequent delivery. A second goal of this invention is to reduce leakage incurred when dispensing materials from a rigid cannula by improving the fit and fill of the annular wall defect.
2. Related Art
Some techniques for nucleus pulposus injection of materials like the SINUX® silicone disc augmentation material, utilize an injection cannula of rigid outer diameter to insert into the annular wall defect. Determination of the excised nucleus pulposus tissue is currently attempted via weight and/or volumetric measurement of the tissue following removal. Corresponding amounts of nucleus replacement material are injected into the disc space. Leakage of the injected material is a known issue when excess nucleus pulposus replacement material is added, correspondingly inadequate replacement of the nucleus can allow for device expulsion or improper functional spinal unit balance. Therefore accurate determination of the removed nucleus pulposus volume remains to be a challenge. Another issue present is the potential leakage of the injected material that may arise from an inadequate fit between the rigid injection cannula and the varying size annular wall defect(s).
Several nucleus pulposus and annular repair patents have been applied and issued. U.S. Patent Application Publication No. 2004/0068268 discloses cannulated distractors for maintaining disc height during replacement or augmentation of the spinal disc. U.S. Patent Application Publication No. 2003/0220649 describes interior liners and membranes such as balloons for in situ formation of nucleus replacement or augmentation materials. Bao et al. (European Cells and Materials, Vol. 10 Suppl. 3, 2005, p. 3), disclose assessing the shape and volume of the nucleus cavity in total nucleus removal procedures using an imaging balloon filled with contrast medium and fluoroscopic balloon images taken from multiple directions. However, none have been found that teach annular sealing for volumetric determination of the evacuated disc space and/or subsequent delivery of the disc replacement or augmentation material as hereinafter disclosed.